In order to improve recording performance of information, various improvements have been made in a magnetic head to be used for a magnetic recording/reproducing apparatus such as a hard disk drive (HDD). For example, Japanese Unexamined Patent Application Publication No. 2005-293822 discloses a technology of increasing the strength of a recording magnetic field, wherein an upper face of a recording magnetic pole and an opposing lower face of a trailing shield are provided with a taper on the side of an ABS so that a leakage magnetic flux to the trailing shield can be inclined toward a recording medium. On the other hand, Japanese Unexamined Patent Application Publication No. 2009-64539 discloses a technology of gently increasing the thickness of a magnetic pole layer rearward from an ABS so as to reduce a leakage magnetic flux from a magnetic pole.
According to the former technology, however, the tapered face of the magnetic pole is wholly opposed to the trailing shield, which excessively generates a leakage magnetic flux from the magnetic pole to the trailing shield. According to the latter technology, on the other hand, the magnetic pole is formed with a tapered face whose inclination angle varies in a stepwise fashion or the magnetic pole is formed with a curved face instead of the tapered face, so that as a result of obtaining a magnetic pole layer whose thickness varies gently, an area of the magnetic pole opposed to the trailing shield inevitably increases to cause a similar problem.
If a large amount of magnetic flux leaks to the trailing shield, as described above, the trailing shield easily causes magnetic saturation, so that the recording magnetic field from the magnetic pole to the magnetic recording medium cannot have a sufficient magnetic field gradient. In general, the magnetic field gradient has a great impact on recording performance of information, and it is known that the larger the magnetic field gradient, the lower the jitter of a magnetic transition region between bits of information to be recorded on the magnetic recording medium, making a boundary of the region clear, which results in achieving excellent bit error rate.